imx28 power off with USB connected

[dragan_s]

Hi,

I have the following scenario:

imx28 is connected to a battery and to a 5V USB power supply.

Powering off the chip via the HW_POWER_RESET_PWD bit causes the device to automatically restart if the USB power supply is still present.

I do not have the possibility to disable the 5V USB supply from software and I do not want to blow the DISABLE_RECOVERY_MODE OTP bit because at some point we may need recovery mode.

Question: how would you prevent the chip to boot if USB 5V is present?

I tried waiting for PSWITCH in XLDR if the start-up source is the 5V and only resume boot if PSWITCH LSB is high but this consumes about 10 mA from the battery and this is too much.

[Yuri · Accepted solution]

In order to power off the i.MX28, the VDD5V should be switched off.

In other case, the situation when internals of i.MX28 are off, but an external

5V is present, is treated as 5V insertion and internal POR is generated,

providing start up sequence again.